The present invention relates to magnetic heads, and more particularly, this invention relates to lead overlay read heads having magnetically pinned passive regions.
One well known way to increase the performance of hard disk drives is to increase the areal data storage density of the magnetic hard disk. This can be accomplished by reducing the written data track width, such that more tracks per inch can be written on the disk. To read data from a disk with a reduced track width, it is also necessary to develop sufficiently narrow read head components, such that unwanted magnetic field interference from adjacent data tracks is substantially eliminated.
The standard prior art read head elements include a plurality of thin film layers that are deposited and fabricated to produce a GMR read head, as is known to those skilled in the art. Significantly, where the width of the thin film layers that comprise the GMR read head is reduced below certain values, the magnetic properties of the layers are substantially compromised. To overcome this problem, GMR read heads have been developed in which the thin film layers have an ample width and the electrical leads are overlaid on top of portions of the thin film layers. This lead overlaid configuration has the effect of creating an active read head region having a width that is less than the entire width of the deposited layers, such that the magnetic properties of the thin film layers can be preserved. Thus, in the lead overlaid GMR read heads of the prior art, active magnetic layer portions exist between the electrical leads and passive magnetic layer portions exist beneath the electrical leads.
A problem that has been recognized with regard to such prior art lead overlaid read heads is that the passive region of the magnetic layers of the read head, and particularly the free magnetic layer, is not entirely passive. That is, external magnetic fields, such as from adjacent data tracks, create magnetic field fluctuation and noise within the passive regions of the free magnetic layer beneath the electrical leads. Thus, noise and side reading effects continue to be a problem with lead overlaid GMR read heads.
Further, prior art heads have hard bias material on either side of the sensor to exert magnetic force on the free layer to magnetically stabilize the free layer. The problem is that hard bias layers are very thick, and as track sizes shrink, sensors must get smaller. When the track width becomes very narrow, the hard bias layers makes the free layer very insensitive and thus less effective. What is needed is a way to create a sensor with a narrow track width, yet with a free layer that is very sensitive
The present invention seeks to solve the aforementioned problems by pinning the magnetization of the free magnetic layer in the passive regions beneath the overlaid electrical leads, thus stabilizing the passive regions, and reducing noise and side reading effects. The embodiments of the present invention provides a sensor with sensitivity that is greatly enhanced over sensors of comparable track width created using prior art methods.
The present invention overcomes the drawbacks and limitations described above by providing a magnetic head having a sensor with a free layer, a spacer layer coupled to the free layer, and a pinned layer coupled to the spacer layer. Each layer has an active portion defined between its end portions. The active portion should correspond roughly to the track width of the media. Leads are coupled to the sensor, with each lead overlapping the end portions of the layers. Preferably, each lead tapers towards the sensor.
The pinned layer is operative to substantially pin magnetic moments of the end portions of the free layer, thereby essentially desensitizing the end portions of the free layer and making hard bias elements unnecessary in this structure. Preferably, the magnetic moments of the end portions of the free layer are antiparallel to moments of the end portions of the pinned layer.
The magnetic moment of the active portion of the pinned layer is less than the magnetic moments of the end portions of the pinned layer, allowing the magnetic moment of the active portion of the free layer to spin freely. The magnetic moment of the active portion of the pinned layer can be reduced by oxidizing that portion of the pinned layer.
Preferably, the free layer and/or the pinned layer are composed of at least FeN. Also preferably, the spacer layer includes at least Cr.
A thickness of the pinned layer in a direction perpendicular to the adjoining surfaces of the pinned layer and the spacer layer is preferably less than a thickness of the free layer in a direction perpendicular to the adjoining surfaces of the pinned layer and the spacer layer. Ideally, the thickness of the pinned layer is less than 75% of the thickness of the free layer, and is possible because of the high magnetic moment of FeN. This provides a great advantage over the prior art in that head size is significantly reduced.
The magnetic head may also include a write portion coupled to the sensor.
To create a head having the structure described above, several layers are deposited to form a sensor. The layers include a free layer, a pinned layer, and a spacer layer between the free layer and pinned layer. Leads are coupled to the sensor (such as by depositing the leads) such that each lead overlaps opposite end portions of the layers. An active portion of the pinned layer is oxidized for reducing its magnetic moment and electrical conductivity, where the active portion is defined between the end portions of the pinned layer. Additional layers may also be added.